Consider each of the questions under I.The metre stick is supported as in I but the support is asymmetric. Conjecture on what will happen if the fingers are moved away from each other.What now will happen? Consider doing it with a baseball bat. Suppose in all of this the metre stick is not uniform.Can you conjure up a situation where, with symmetric supports to begin with, the supports will not meet in the middle?.Suppose the fingers are replaced by two supports of enequal roughness, say an iron rod and a wooden stick or a rubber rod.What now is the question to ask? And how is it answered? Why is this the answer?.What condition must be met for the fingers to experience identical motion?.When the fingers are pushed towards each other what forces now exist at each finger?.When at rest what force is supplied by each finger?.The fingers are pushed toward each other. Here is a presentation of this demonstration by Julius Sumner Miller (Demonstrations in Physics pages 16 and 17):Ī metre stick is supported horizontally on two fingers symmetrically placed. Using a 1-kg weight on the end moves the centre-of-gravity to 70 cm from the end. (Optional) Repeat steps 1 through 4 above using an 8-foot length of 2" x 2" in place of the metre stick.Repeat steps 1 through 4 using a plexiglass cylinder and a cork covered piece of wood instead of your fingers to show this works when the coefficients of friction of the supports are different.The centre-of-gravity has moved because of the weight and your fingers will come together on the side with the weight. Place a 200-g weight on one end of the metre stick.Your fingers will alternate between slipping and sliding along the stick and will come together at 50 cm, the centre-of-gravity. Place the metre stick on your forefingers with one finger at 0 cm and one at 100 cm.Optional: an 8-foot length of 2" x 2" and a 1-kg weight.
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